How to: Replace an AC Compressor from a GM 3100 engine

These instructions are for any GM car with the 3100 engine, with air conditioning. (Engine code: M) These engines are found in the 1994-1996 Chevrolet Corsica, among other cars and years.

Some background info: The AC Compressor is held up with 3 LONG bolts. I’m not talking little things, I’m talking 4″ bolts.

TAKE YOUR CAR TO A SHOP AND GET THEM TO REMOVE THE REFRIGERANT.

Jack up the car.

3) Remove the passenger’s side splash guard. That’s the one in front of the wheel, there are 3 or 4 bolts holding it in place in the wheel well, and 2 or 3 underneath the car. After they’re off, the guard should just sorta flap around, because it’s still semi-permanently attached to the top of the wheel well. Fine. I don’t care.

Remove the serpentine belt.

Get back under the car and find the AC Compressor. It shouldn’t be hard to find, it’s the thing on the serpentine belt closest to the bottom of the car (it should be right in your face), and has AC pipes connected to it.

Remove the AC Clutch plug, there are little tabs on both sides (Front and back) that hold it in. You have to pull those away from the connector and then pull the connector away from the compressor.

You should see the two AC pipes that connect to the compressor, with a bolt in the middle. One is the high-pressure, and one is the low-pressure. SLOWLY remove that bolt, and if it starts to hiss, STOP. If you got the refrigerant removed properly, the pressure (if any) should be compressed air from the compressor running on empty. Let it hiss out. Once it’s done, remove the bolt, and cover the pipe connectors with a cloth or something. You don’t want to get them dirty.

You should see two screws. One is a big long one, angled towards the engine block. You want to unscrew that one. The other one is the oil drain for the compressor. If you unscrew that one, it makes a big mess. Trust me. If you unscrew it and find it’s only a 2″ long screw, PUT IT BACK.

Now, from above (Yes, get out from under the car for this)… There are two bolts on the upper side. On my car, they were right smack-dab behind a coolant hose. The hose was flexible enough i just sorta pushed it out of the way. Remove those two bolts, be careful on the last one, cause the whole thing will drop somewhat.

Get back under the car, and manouver the thing out through the bottom. It’s at least a good 20 pounds, don’t drop it on the ground or on your face. The first would be bad for the compressor, the second would be bad for your complexion.

Look around for where the little dog-bone extension went to, it probably fell somewhere after you took out the last bolt. This guy holds the compressor away from the engine so there’s room in between the two.

“Installation is reverse of removal”

About the picture: Here it is, upside-down. I’ve circled the part number of the compressor assembly in red. This is what you need to get yourself a new or used one. (IE, this is the number that carpart.com asks for)

I originally posted this article on Corsicas.com on January 18, 2006. To see original text, click here